As per what have been acknowledged, the structure of a conventional torque wrench, as shown in FIGS. 11 and 12, comprises a wrench 7, a mark plate 8 and an indicator 9. The wrench 7 is formed by a wrench body 70 with a handle 71 at one end and a wrench head 72 at the other end. A driving head 73 is formed as one piece with the wrench head 72 for lodging into a work piece or a sleeve, and a fixing hole 720 is implemented on the wrench head 72. The mark plate 8 is firmly fixed on the wrench body 70 near the handle 71 and has notched torque scales 80 put onto. The indicator 9 is fixed on the fixing hole 720 at one end and extends to above the mark plate 8 at the other end.
However, since the wrench head 72 and the driving head 73 of the conventional torque wrench are formed as one piece, when the driving head 73 is lodged into a bolt assembly or a sleeve and then turned to certain degree of angle, the user has to take out the driving head 73 from the hole, turn it backward to certain degree of angle, and then lodge it back to the bolt or the sleeve for applying force on turning the wrench, which is presumed in such a way time and energy consuming and giving influence to working efficiency.